Pertussis is disease entity that affects all populations but can cause severe morbidity and mortality in the infant population. Although mass immunization has decreased the incidence of pertussis, immunity wanes with increasing age. When infected this age group may have mild symptomatology often attributed to more common etiologies. This prospective observational study will attempt to determine the prevalence of pertussis in adolescents and young adults aged 10-25 years with a cough of six days duration who present to the Bellevue Hospital Pediatric Emergency Room or Adolescent Clinic.